Dielectric waveguide mixer and dielectric waveguide radar module

ABSTRACT

A non-radiative dielectric waveguide mixer includes at least one conductive plate, a dielectric waveguide held on said conductive plate and a solid-state device disposed across said dielectric waveguide for mixing at least two high-frequency signals which are propagated in opposite directions along said dielectric waveguide. The non-radiative dielectric waveguide mixer may be combined with a high-frequency signal generator and an antenna mechanism to provide a non-radiative dielectric waveguide radar module.

This is a divisional of co-pending application Ser. No. 08/180,995,filed on Jan. 13, 1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dielectric waveguide radar module foruse as a component in a millimeter wave radar device installed on amotor vehicle, and more particularly to a dielectric waveguide mixer foruse in such a radar module.

2. Description of the Prior Art

Radar devices for use on motor vehicles such as automobiles incombination with warning units for preventing collisions are required tohave a high degree of resolution for detecting objects at closedistances, for example, at distances of up to about several decimeters.In view of this high-resolution requirement, FM radar systems arepreferred over pulsed radar systems for use in vehicle-mountedapplication. Since the maximum range to a target, such as a precedingmotor vehicle or an upcoming motor vehicle, that may be detected is arelatively short distance, roughly several hundred meters, it issuitable for vehicle-mounted radar systems to use radiowaves in themillimeter range. These waves have a frequency of about 60 GHz and canbe attenuated greatly upon propagation in order to prevent propagationbeyond a necessary range and also to minimize interference with existingmicrowave communications equipment. Use of millimeter waves is alsopreferable from the viewpoint of reducing the size of a radar modulewhich may include an antenna, FM signal generators in front and rearstages, a mixer, and other components.

Heretofore, FM radar modules in the millimeter range have beenconstructed in the form of a microstrip waveguide or a waveguide.Because microstrip waveguides radiate a large amount of power, theysuffer a large loss, and interference tends to result between multipleof modules. This results in a reduction in measuring accuracy. Aconventional waveguide is disadvantageous in that its circuit is largein size and expensive.

One attempt to solve the above problems is illustrated by anon-radiative dielectric waveguide such as that disclosed as in thearticle "Millimeter wave integrated circuit using a non-radiativedielectric waveguide" written by Yoneyama et al. and published in theJournal of Electronic Information Communications Society, Vol. J 73 C-1,No. 3, pp. 87 94, March 1990. The disclosed non-radiative dielectricwaveguide comprises two confronting conductive plates spaced from eachother by a distance slightly smaller than a half wavelength and arod-shaped, dielectric member inserted between the conductive plates forallowing propagations only along the rod-shaped dielectric member. Theupper and lower surfaces of the non-radiative dielectric waveguide arecompletely shielded by the conductive plates. Since the distance betweenthe conductive plates is shorter than a half wavelength, radiowaves areprevented from leaking laterally out of the non-radiative dielectricwaveguide. Therefore, any power radiation from the non-radiativedielectric waveguide is very small, effectively avoiding interferencebetween multiple modules and also radiation loss in each module. Variouscomponents including a directional coupler and an isolator can easily befabricated by positioning non-radiative dielectric waveguides closely toeach other or adding ferrite. Therefore, a plurality of high-frequencyfunctional components can be fabricated between two flat metal plates,making it possible to reduce the overall size of a module to such anextent which is comparable with conventional microwave IC (MIC).

The above article also discloses transmitter and receiver structures foruse in the millimeter wave band which employ non-radiative dielectricwaveguides. The radar module disclosed in the above article has aproblem in that its overall size is large because its transmitter andreceiver are of separate structures. Further, it is difficult to reducethe-size of the disclosed radar module. This makes it difficult todispose such a device in a door or a bumper of an automobile.

Since the transmitter and receiver of the disclosed radar module areseparate structures, each of the transmitter and receiver must have ahigh-frequency generator of its own, making the radar module expensive.The radar module is designed as a Doppler radar using a constant wave(CW) of a constant frequency. However, such a radar arrangement cannotbe applied to an FM radar system for detecting the positions (bearingand relative distance) of obstacles which may exist around theautomobile.

The above article further shows a single balanced mixer. While thesingle balanced mixer is advantageous in that it suffers low noise, thecost of its parts is high and it is difficult to reduce the size of themodule employing the same because the mixer employs two diodes of thesame characteristics and requires impedance matching. In order toachieve impedance matching between the waveguide and two diodes havingthe same characteristics, it is necessary to carry out a complexadjusting process of varying the air gap and the thickness of a thinfilm having a high dielectric constant. Since it is very difficult toeffect such an adjusting process, the adjusting process may producenonuniform characteristics in radar modules and reduce the rate of massproduction of radar modules. The balanced mixer requires, in principle,that a local signal be divided and supplied to the mixer diodes.Therefore, the balanced mixer should be supplied with a local signal ofconsiderably high power in order to produce an output signal of adesired level. In the case where a homodyne radar system with a singlehigh-frequency generator is designed, the output signal transmitted fromthe transmission antenna is decreased by an amount commensurate with theassigned energy, since a considerable proportion of the output signalfrom the generator has to be assigned to the local signal. As aconsequence, the maximum distance that can be covered by the radarsystem is reduced.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide adielectric waveguide mixer and a dielectric waveguide radar module whichare made up of a reduced number of parts, are small in size, and provideimproved performance.

According to the present invention, there is provided a dielectricwaveguide mixer comprising at least one conductive plate, a dielectricwaveguide held on the conductive plate, and a solid-state devicedisposed across the dielectric waveguide for mixing at least twohigh-frequency signals which are propagated in opposite directions alongthe dielectric waveguide.

An FM radar module which incorporates the above dielectric waveguidemixer comprises at least one conductive plate, high-frequency signalgenerating means held on the conductive plate for generating ahigh-frequency signal, antenna means for radiating out thehigh-frequency signal, propagating means for propagating signals, thepropagating means having at least a dielectric waveguide held on theconductive plate and connected between the high-frequency signalgenerating means and the antenna means, for propagating, in a firstdirection, a high-frequency signal generated by the high-frequencysignal generating means to the antenna means for radiation therefrom andpropagating, in a second direction opposite to the first direction, asignal reflected by an external object to which the high-frequencysignal is radiated and received by the antenna means, and mixer meansdisposed across the dielectric waveguide for mixing the signalspropagated in the first and second directions into a beat signal.

With the above arrangement, a high-frequency signal (FM signal) in themillimeter wave band generated by the high-frequency signal generatingmeans signal generator is supplied through a non-radiative dielectricwaveguide as the propagating means to the antenna means, e.g., a commontransmission and reception antenna, by which the signal is radiated. Asignal reflected by an object is received by the transmission andreception antenna and propagated through the non-radiative dielectricwaveguide in a direction opposite to the direction in which thehigh-frequency signal is propagated to the transmission and receptionantenna. The mixer means, e.g., a single-diode mixer, is disposed acrossthe non-radiative dielectric waveguide. The single-diode mixer issupplied with two oppositely directed high-frequency signals, i.e., thesignal propagated to the-common transmission and reception antenna andthe signal received thereby, and mixes the supplied high-frequencysignal into a beat signal having a certain frequency.

If the high-frequency signal generating means is an FM signal generator,then the frequency of the beat signal represents the period of time overwhich the FM signal travels from the antenna to an object and back. Thisperiod may be used to calculate the distance to the object. If thehigh-frequency signal generating means is a high-frequency signalgenerator for generating a high-frequency signal having a constantfrequency, then the frequency of the beat signal represents the relativespeed with respect to the object. The dielectric waveguide mixer or theradar module which incorporates the dielectric waveguide mixer may besmall in size as the single-diode mixer for mixing the oppositelydirected high-frequency signals is disposed in a certain position on thenon-radiative dielectric waveguide.

When the single-diode mixer is positioned across the non-radiativedielectric waveguide, the single-diode mixer is laterally offset fromthe position where the maximum electric field intensity in an LSMO1 modein the non-radiative dielectric waveguide is exhibited for achievingimpedance matching between the single-diode mixer and the non-radiativedielectric waveguide. Unlike the conventional process of achievingimpedance matching between a mixer and a dielectric waveguide, thedielectric waveguide mixer or radar module of the present inventionrequires no thin film having a high dielectric constant and no air gapsfor impedance matching, thus minimizing process characteristicvariations of manufactured dielectric waveguide mixers or radar modules.The single-diode mixer which employs such an impedance matching processmay be reduced in size, This allows the radar module to be reduced inoverall size and reduces variations in radar module characteristics,because it is not necessary to match the characteristics of two diodeswhich would otherwise be necessary.

The above and further objects, details and advantages of the presentinvention will become apparent from the following detailed descriptionof preferred embodiments thereof, when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a dielectric waveguide radar module accordingto a first embodiment of the present invention;

FIG. 2(a) is a plan view of a dielectric waveguide radar moduleaccording to a second embodiment of the present invention;

FIG. 2(b) is a side elevational view of the dielectric waveguide radarmodule shown in FIG. 1(a);

FIG. 3 is an enlarged fragmentary plan view of a single-diode mixer andits associated components in the dielectric waveguide radar module shownin FIG. 2(a);

FIG. 4 is an enlarged front elevational view of the single-diode mixerand its associated components in the dielectric waveguide radar moduleshown in FIG. 2(a); and

FIG. 5 is a plan view of a modification of the dielectric waveguideradar module shown in FIG. 2(a).

FIGS. 6(a)-6(e) illustrate various embodiments of single plate opendielectric waveguides.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A dielectric waveguide radar module, shown in FIG. 1, according to afirst embodiment of the present invention is designed such that it issmaller as a whole than a conventional radar module having a separatetransmitter and receiver as disclosed in the above article, isconfigured for easy installation on a mobile object such as anautomobile, employs a single high-frequency generator, and comprises ahomodyne radar system for overall cost reduction.

As shown in FIG. 1, the dielectric waveguide radar module basicallycomprises a non-radiative dielectric waveguide having a linear or curveddielectric rod inserted between upper and lower parallel conductiveplates 30. The dielectric waveguide radar module also includes ahigh-frequency generator 31 comprising a gunn diode and a varactor diodefor generating a high-frequency FM signal, an isolator 32, directionalcouplers 33 and 36, a transmission antenna 34, a reception antenna 35,and a single balanced mixer 37. The directional coupler 33 comprisesfirst and second dielectric rods which are disposed closely to eachother, the first dielectric rod being connected to the isolator 32 andthe second dielectric rod being connected to the transmission antenna34. The directional coupler 36 comprises the first dielectric rod and athird dielectric rod which are disposed closely to each other, the thirddielectric rod being connected to the reception antenna 35.

An FM signal in the millimeter wave band which is generated by thehigh-frequency generator 31 passes through the isolator 32, after whichabout a half of the electric power of the FM signal is supplied throughthe directional coupler 33 to the transmission antenna 34. The FM signalsupplied to the transmission antenna 34 is radiated as a transmittedsignal into ambient space. A signal that is reflected by an object thatexists in the ambient space is received by the reception antenna 35. Thereceived signal is supplied through the directional coupler 36 to twomixer diodes of the single balanced mixer 37. At this time, the signalreflected by the object is also received by the transmission antenna 34,and sent by the isolator 32 as an unwanted signal to a resistiveterminator 38, which converts the signal into heat that is dissipated.The remaining energy of the FM signal that is supplied to thedirectional coupler 33 is applied as a local signal to the directionalcoupler 36, which divides the signal into two halves that are suppliedto the respective diodes of the single balanced mixer 37. The singlebalanced mixer 37 mixes the received signal with the local signal,producing a beat signal having a frequency which represents the relativedistance between an object and the radar module.

An FM radar module according to a second embodiment of the presentinvention will be described below with reference to FIGS. 2(a) and 2(b).The FM radar module according to the second embodiment is effective tosolve a number of problems suffered by conventional balanced mixers.

As shown in FIGS. 2(a) and 2(b), the FM radar module comprises an upperconductive plate 1, a lower conductive plate 2, a high-frequency signal(FM signal) generator 3, dielectric waveguides 4, 6, 7, 8 serving asnon-radiative dielectric waveguide means for propagating ahigh-frequency signal, a circulator 5, a resistive terminator 8, acommon transmission and reception antenna horn 9a, a reflector 9b, and asingle-diode mixer 10.

The high-frequency signal generator 3 comprises a gunn diode mount 3a,such as a metal block a microstrip line 3b held on a side surface of thegunn diode mount 3a and supporting thereon a gunn diode for generating ahigh-frequency signal and a varactor diode for modulating a frequency;and a metal strip 30 doubling as a resonator for guiding ahigh-frequency signal (FM signal) generated by the gunn diode on themicrostrip line 3b to the non-radiative dielectric waveguides, includingthe dielectric waveguide 4. The metal strip 3c may comprise a thin filmor a metal rod.

The upper and lower conductive plates 1 and 2 lie parallel to each otherand are spaced from each other by a distance that is slightly smallerthan one half of a wavelength of the FM signal in the millimeter waveband that is generated by the gunn diode. Therefore, the FM signal canbe propagated only along the dielectric waveguides between the upper andlower conductive plates 1 and 2. The FM signal is propagated in twomajor propagation modes, i.e., an LSMO1 mode and an LSEO1 mode. In orderto suppress the LSMO1 mode that is of low logs, a mode suppressor may beembedded in a certain location in the dielectric waveguides. As shown inFIG. 2(b), the lower conductive plate 2 is supported on a support plate2(a) by a plurality of support columns 1(b).

As shown in FIGS. 3 and 4, the single-diode mixer 10 does not requireair gaps or thin films of a high dielectric constant on its front andrear ends for impedance matching. The dielectric waveguides 6 and 7 haverespective portions of constant width and height that are positioned oneon each side of a dielectric substrate 11 on which a mixer diode 12 ismounted, the portions of the dielectric waveguides 6 and 7 havingvertical end surfaces held against the dielectric substrate 11.

Diode attachment patterns 15 are juxtaposed on a central region of thedielectric substrate 11 at one surface thereof and spaced from eachother. The mixer diode 12 has its terminals connected to the respectivediode attachment patterns 15 such that the mixer diode 12 is laterallyoffset a distance d from the center of the dielectric substrate 11.Specifically, the mixer diode 12 is laterally spaced the distance d fromthe position where the maximum electric field intensity in the LSMO1mode in the dielectric waveguide 6 is exhibited. The impedance matchingbetween the dielectric waveguides 6 and 7 and the mixer diode 12 can beachieved by adjusting the distance d and optimizing the area and shapeof the diode attachment patterns 15, without any air gaps or thin filmsof a high dielectric constant.

A plurality of parallel diodes may be disposed on the diode attachmentpatterns 15, or a solid-state device of the same function as the diode12 may be employed in place of the diode 12. The diode attachmentpatterns 15 may be mounted on opposite surfaces of the dielectricsubstrate 11, and mixer diodes 12 may be mounted on the diode attachmentpatterns 15 on each surface of the dielectric substrate 11.

The distance d and the area and shape of the diode attachment patterns15 may be selected to control the ratio of the electric power of anelectromagnetic wave A that is transmitted through the single-diodemixer 10 and the electric power of an electromagnetic wave B that isconverted by the single-diode mixer 10.

To the diode attachment patterns 15, there are connected respectivelytwo 1/4 choke patterns for preventing the high-frequency signal fromleaking from the non-radiative dielectric waveguide and also forsupplying a bias voltage to the mixer diode 12. The beat signal that isconverted by the single-diode mixer 10 and from which undesiredhigh-frequency signal is removed by the 1/4 choke patterns is suppliedto an external circuit through a lead 14.

In the non-radiative dielectric waveguide shown in FIG. 2(a), thedielectric waveguides 5 and 7 have a common transmission and receptionantenna 9 on one end thereof and have the single-diode mixer 10 disposedintemediately between them. The dielectric waveguide 4 has ahigh-frequency signal generator 3 disposed on one end, and thedielectric waveguide 8 has a resistive terminator 8' disposed on oneend. The other ends of the waveguides 4, 6 and 8 are connected to thecirculator 5 such that the dielectric waveguides 6 and 4 extend radiallyoutwardly from the centrally located circulator 5 between the parallelconductive plates 1 and 2. An FM signal in the millimeter wave band thatis generated by the FM signal generator 3 is propagated through thenon-radiative dielectric waveguide including the dielectric waveguide 1to the circulator 5, which leads the FM signal to the non-radiativedielectric waveguide including the output dielectric waveguide 6. The FMsignal reaches the single-diode mixer 10 that is positioned across theoutput dielectric waveguide 6. Most of the electric power of the FMsignal is transmitted through the single-diode mixer 10 and radiated outfrom the common transmission and reception antenna 9. The remainingelectric power is absorbed as a frequency-converting local signal intothe single-diode mixer 10.

As shown in FIGS. 2(a) and 2(b), the common transmission and receptionantenna 9 comprises a horn antenna 9a having an opening that is linearlyenlarged from its base. The antenna 9a is and connected to the parallelconductive plates 1 and 2 toward its distal end. A parabolic reflector9b is disposed in front of the horn antenna 9a. The horn antenna 9a andthe parabolic reflector 9b jointly serve to radiate the FM signal thathas been propagated through the non-radiative dielectric waveguide tothe dielectric waveguide 7 joined to the dielectric waveguide 6. Theradiated FM signal is reflected by an object, and the reflected signalis received by the parabolic reflector 9b and the horn antenna 9a, andguided to the dielectric waveguide 7. Thereafter, the received signal ispropagated through the non-radiative dielectric waveguide including thedielectric waveguide 6 to the single-diode mixer 10.

More specifically, a portion of a high-frequency signal generated by thehigh-frequency signal generator 3 is propagated through the dielectricwaveguide 4, the circulator 5, and the dielectric waveguide 6 to thesingle-diode mixer 10, and the remaining portion of the high-frequencysignal is transmitted through the mixer 10 and radiated through thecommon transmission and reception antenna 9. The radiated high-frequencysignal is reflected by an object, and received by the commontransmission and recaption antenna 9. A portion of the received signalis propagated through the dielectric waveguide 6 to the mixer 10 whereit is mixed with the portion of the high-frequency signal that has beenpropagated through the dielectric waveguide 4, the circulator 5, and thedielectric waveguide 6 to the single-diode mixer 10. The remainingportion of the received signal is transmitted through the mixer 10 andthe dielectric waveguide 8 to the resistive terminator 8', which absorbsthe energy of the supplied signal.

As described above, the single-diode mixer 10 is supplied with signalspropagated in opposite directions, i.e., the FM signal to be radiatedthrough the common transmission and reception antenna 9 and the signalreflected by the object and received by the common transmission andreception antenna 9. The mixer 10 mixes the supplied signals into a beatsignal having a low frequency ranging from several tends of KHz toseveral MHz. The beat signal is then supplied through the lead 14 to acircuit external to the radar module. The remaining portion of thereceived signal that is transmitted through the mixer 10 is propagatedthrough the circulator 5 and the non-radiative dielectric waveguideincluding the dielectric waveguide 8 to the resistive terminator 8' forenergy absorption.

Turning now to a second embodiment shown in FIG. 5, a radar module whichincludes the non-radiative dielectric waveguide mixer 10 may beincorporated in a radar module having a transmission antenna and areception antenna that are separate from each other. For example, FIG. 5shows a modified radar module having a transmission antenna 17 and areception antenna 16 that are separate from each other, the transmissionantenna 17 being coupled to the dielectric waveguide 6 through adirectional coupler 18. A portion of a signal that is supplied toantenna 17 is separated by the directional coupler 18. The separated FMsignal is propagated through the non-radiative dielectric waveguide tothe single-diode mixer 10. A reflected signal received by the receptionantenna 16 is propagated through the dielectric waveguide 6 to thesingle-diode mixer 10.

More specifically, a portion of a high-frequency signal generated by thehigh-frequency signal generator 3 is propagated through the dielectricwaveguide 4, the circulator 5, and the dielectric waveguide 6 to thesingle-diode mixer 10, and the remaining portion of the high-frequencysignal is propagated from the dielectric waveguide 6 through thedirectional coupler 18 to the transmission antenna 17, which radiatesthe high-frequency signal. The radiated high-frequency signal isreflected by an object, and received by the reception antenna 16. Aportion of the received signal is propagated to the mixer 10 where it ismixed With the portion of the high-frequency signal that has beenpropagated through the dielectric waveguide 4, the circulator 5, and thedielectric waveguide 6 to the single-diode mixer 10. The remainingportion or the received signal is transmitted through the mixer 10, thedielectric waveguide 6, the circulator 5, and the dielectric waveguide 8to the resistive terminator 8', which absorbs the energy of the suppliedsignal.

According to the modified radar module shown in FIG. 5, the transmissionantenna 17 has an antenna radiation pattern 17' and the receptionantenna 16 has an antenna reception pattern 16'. Therefore, the range inwhich objects can be detected by the modified radar module is indicatedas a hatched range 20 where the antenna patterns 16' and 17' overlapeach other. With the common transmission and reception antennas 17 and16 being independent of each other, the modified radar module provides ahypothetical detection pattern 20 which is laterally narrower than theindividual transmission and reception antennas 17 and 16. Consequently,the modified radar module has a high resolution in the lateraldirection. For a radar with high hearing resolution, the radar moduleshown in FIG. 5 is preferable to the radar module shown in FIGS. 2(a)and 2(b).

In the second embodiment, the single lead 14 is used as a line forsupplying a bias voltage to the single-diode mixer 10 and loading a beatsignal to an external circuit. However, considering the frequency of thebeat signal, the lead 14 may be replaced with a coaxial cable or thelike.

In each of the above embodiments, a high-frequency signal generator inthe form of an FM signal generator may be replaced with a signalgenerator which generates a signal having a constant frequency toprovide a Doppler radar module that is capable of detecting a speedActive to an object from a beat frequency. The high-frequency signalgenerator may be operated selectively in an FM (frequency-swept) mode oran FM (frequency-fixed) mode at different times for detecting relativedistance and speed in a time-division multiplex fashion.

According to the present invention, as described above, the dielectricwaveguide mixer as it is incorporated in the dielectric waveguide radarmodule has a single-diode mixer disposed in and across the dielectricwaveguide which propagates, in opposite directions, a high-frequencysignal supplied from the high-frequency signal generator to thetransmission antenna and a high-frequency signal reflected by an objectand received by the reception antenna. With this arrangement, the numberof parts of the dielectric waveguide radar module and the size thereofare reduced. Use of the common transmission and reception antenna iseffective to further reduce the size of the dielectric waveguide radarmodule, and increase the maximum detectable distance as the electricpower of a local signal may be low.

Unlike the conventional single balanced mixer, the dielectric waveguidemixer according to the present invention is capable of achievingimpedance matching without any air gaps and thin films of a highdielectric constant, and is hence freed from a complex adjusting processfor impedance matching. Therefore, the dielectric waveguide mixeraccording to the present invention allows simple small-size radarmodules of uniform characteristics to be fabricated on a mass-productionbasis.

While the dielectric waveguide mixer and the dielectric waveguide radarmodule have been described as employing the non-radiative dielectricwaveguide in the above embodiments, the waveguide used is not limited tothe non-radiative dielectric waveguide, but may be a dielectricwaveguide such as an H guide or an insular waveguide. Further, as shownin FIGS. 6(a)-6(e), the dielectric waveguide may comprise a singleconductive plate. The structures shown in FIGS. 6(a)-6(e) can be groupedinto two categories: strongly guiding and weakly guiding. The structuresillustrated in FIGS. 6(a)-6(c) comprise modifications of dielectric rodsof rectangular cross-sections and include a rectangular rod waveguide(FIG. 6(a)), an image line (FIG. 6(b)), and a trapped image line (FIG.6(c)). The structures illustrated in FIGS. 6(d) and 6 (e) comprise aninsulated image line (FIG. 6 (d)) and an inverted strip line (FIG.6(e)), and are formed by a dielectric strip that perturbs a planardielectric waveguide.

The high-frequency signal generator is not limited to the gunn diode,but may be any of various other solid-state oscillating elementsincluding an IMPATT diode, a TUNNET diode, a BARIT diode, a TRAPETTdiode, an LSA diode, etc.

The dielectric waveguide mixer according to the present invention may beincorporated in general frequency converters including an upconverter, adownconverter, etc., rather than the radar module.

Although there have been described what are at present considered to bethe preferred embodiments of the invention, it will be understood thatthe invention may be embodied in other specific forms without departingfrom the essential characteristics thereof. The present embodiments aretherefore to be considered in all respects as illustrative, and notrestrictive. The scope of the invention is indicated by the appendedclaims rather than by the foregoing description.

What is claimed:
 1. A dielectric waveguide radar module comprising:atlease one conductive plate; high-frequency signal generating means heldon said conductive plate, for generating a high-frequency signal;antenna means for radiating out said high-frequency signal; propagatingmeans for propagating signals, said propagating means having at least adielectric waveguide held on said conductive plate and connected betweensaid high-frequency signal generating means and said antenna means, forpropagating, in a first direction, a high-frequency signal generated bysaid high-frequency signal generating means to said antenna means forradiation therefrom and propagating, in a second direction opposite tosaid first direction, a signal reflected by an external object to whichthe high-frequency signal is radiated and received by said antennameans; and mixer means disposed across said dielectric waveguide formixing the signals propagated in said first and second directions into abeat signal.
 2. A dielectric waveguide radar module according to claim1, wherein said antenna means comprises a common transmission andreception antenna.
 3. A dielectric waveguide radar module according toclaim 1, wherein said high-frequency signal generating means comprisesan FM signal generator for generating an FM signal having a varyingfrequency, and means for detecting a distance to said object based on afrequency of said beat signal generated by said mixer means.
 4. Adielectric waveguide radar module according to claim 1, wherein saidhigh-frequency signal generating means comprises a high-frequency signalgenerator for generating a signal having a fixed frequency, and meansfor detecting a speed relative to said object based on a frequency ofsaid beat signal generated by said mixer means.
 5. A dielectricwaveguide radar module according to claim 1, wherein said antenna meanscomprises a common transmission and reception antenna;said propagatingmeans comprises:a first dielectric waveguide having a terminal connectedto said common transmission and reception antenna, said mixer meansbeing disposed on said first dielectric waveguide at an intermediateposition thereof; a second dielectric waveguide having a terminalconnected to said high-frequency signal generating means; a thirddielectric waveguide having a terminal connected to a resistiveterminator; and a circulator connected to opposite terminals of saidfirst, second, and third dielectric waveguides such that said first,second, and third dielectric waveguides are disposed on said conductiveplate and extend radially outwardly from said circulator; thearrangement being such that a first portion of the high-frequency signalgenerated by said high-frequency signal generating means is propagatedthrough said second dielectric waveguide, said circulator, and saidfirst dielectric waveguide to said mixer means, a second portion of thehigh-frequency signal is transmitted through said mixer means andradiated from said antenna means, a first portion of the signalreflected by the object is received by said antenna means, propagatedthrough said first dielectric waveguide to said mixer means, and mixedwith said first portion of the high-frequency signal, and a secondportion of the signal reflected by the object is received by saidantenna means, transmitted through said mixer means, said circulator,and said third dielectric waveguide, and absorbed by said resistiveterminator.
 6. A dielectric waveguide radar module according to claim 1,wherein said antenna means comprises a transmission antenna and areception antenna;said propagating means comprising:a first dielectricwaveguide having a terminal connected to said transmission antenna, saidmixer means being disposed across said first dielectric waveguide; asecond dielectric waveguide having a terminal connected to saidhigh-frequency signal generating means; a third dielectric waveguidehaving a terminal connected to a resistive terminator; a circulatorconnected to opposite terminals of said first, second, and thirddielectric waveguides such that said first, second, and third dielectricwaveguides are disposed on said conductive plate and extend radiallyoutwardly from said circulator; and directional coupling means forcoupling said transmission antenna means between said mixer means andsaid circulator; the arrangement being such that a first portion of thehigh-frequency signal generated by said high-frequency signal generatingmeans is propagated through said second dielectric waveguide, saidcirculator, and said first dielectric waveguide to said mixer means, asecond portion of the high-frequency signal is transmitted from saidfirst dielectric waveguide through said directional coupling means tosaid transmission antenna and radiated from said transmission antenna, afirst portion of the signal reflected by the object is received by saidreception antenna, propagated to said mixer means, and mixed with saidfirst portion of the high-frequency signal, and a second portion of thesignal reflected by the object is received by said reception antenna,transmitted through said mixer means, said first dielectric waveguide,said circulator, and said third dielectric waveguide, and absorbed bysaid resistive terminator.
 7. A dielectric waveguide radar moduleaccording to claim 1, further comprising an upper conductive platedisposed above and extending parallel to said conductive plate whichserves as a lower conductive plate, said antenna means, said propagatingmeans, and said mixer means being held between said upper and lowerconductive plates.
 8. A dielectric waveguide radar module comprising:atleast one conductive plate; high-frequency signal generating means heldon said conductive plate, for generating a high-frequency signal; afirst dielectric rod for propagating the high-frequency signal; a seconddielectric rod disposed closely to said first dielectric rod, said firstand second dielectric rods jointly serving as a first directionalcoupler for dividing a portion of the high-frequency signal; atransmission antenna for radiating out the high-frequency signalpropagated through said second dielectric rod; a reception antenna forreceiving an external signal; a third dielectric rod for propagating asignal received by said reception antenna, said first and thirddielectric rods jointly serving as a second directional coupler; andmixer means for mixing the signal received by said reception antennawith a local signal related to the high-frequency signal radiated bysaid transmission antenna.
 9. A dielectric waveguide radar moduleaccording to claim 8, wherein said high-frequency signal generatingmeans comprises an FM signal generator for generating an FM, signalwhose frequency varies with time.
 10. A dielectric waveguide radarmodule according to claim 9, wherein said signal generator includes avaractor diode.
 11. A dielectric waveguide radar module according toclaim 8, wherein said high-frequency signal generating means comprises ahigh-frequency generator for generating a high-frequency signal whosefrequency is fixed with respect to time.